Argetlam, I didn't really like how he developed the characters. It seemed like John Flanagan made the characters too similar to the Rangers Apprentice characters (Thorn = Halt, Hal = Will, Stig/Ingvar = Horace, Lydia = Evanlyn, etc.), then he realized it and basically stopped the character development.
There were also parts of the plot that I found to be kind of stupid, like why 5+ guards would chase after a single unarmed "boy" (Lydia), and why the Herons would be worried they would be seen if they went into town, even though the Raven had no idea there were even being chased or who their chasers were. I also thought the original few pages when the Herons met Lydia was extremely corny.
I did still like the plot a lot, and the battle in this book was just as magnificent as all the others.